Upgrading to 2.4 from 2.2

In order to assist folks upgrading, we maintain a document
describing information critical to existing Apache HTTP Server users. These
are intended to be brief notes, and you should be able to find
more information in either the New Features document, or in
the src/CHANGES file. Application and module developers
can find a summary of API changes in the API updates overview.

This document describes changes in server behavior that might
require you to change your configuration or how you use the server
in order to continue using 2.4 as you are currently using 2.2.
To take advantage of new features in 2.4, see the New Features
document.

This document describes only the changes from 2.2 to 2.4. If you
are upgrading from version 2.0, you should also consult the 2.0 to 2.2
upgrading document.

See also

The compilation process is very similar to the one used in
version 2.2. Your old configure command line (as
found in build/config.nice in the installed server
directory) can be used in most cases. There are some changes in
the default settings. Some details of changes:

These modules have been removed: mod_authn_default,
mod_authz_default, mod_mem_cache. If you were using
mod_mem_cache in 2.2, look at mod_cache_disk in
2.4.

All load balancing implementations have been moved to
individual, self-contained mod_proxy submodules, e.g.
mod_lbmethod_bybusyness. You might need
to build and load any of these that your configuration
uses.

Platform support has been removed for BeOS, TPF, and
even older platforms such as A/UX, Next, and Tandem. These were
believed to be broken anyway.

configure: dynamic modules (DSO) are built by default

configure: By default, only a basic set of modules is loaded. The
other LoadModule directives are commented
out.

configure: the "most" module set gets built by default

configure: the "reallyall" module set adds developer modules
to the "all" set

Directives that control how authorization modules respond when they don't match
the authenticated user have been removed: This includes
AuthzLDAPAuthoritative, AuthzDBDAuthoritative, AuthzDBMAuthoritative,
AuthzGroupFileAuthoritative, AuthzUserAuthoritative,
and AuthzOwnerAuthoritative. These directives have been replaced by the
more expressive RequireAny,
RequireNone, and
RequireAll.

If you use mod_authz_dbm, you must port your
configuration to use Require dbm-group ... in place
of Require group ....

In 2.2, access control based on client hostname, IP address,
and other characteristics of client requests was done using the
directives Order, Allow, Deny, and Satisfy.

In 2.4, such access control is done in the same way as other
authorization checks, using the new module
mod_authz_host. The old access control idioms
should be replaced by the new authentication mechanisms,
although for compatibility with old configurations, the new
module mod_access_compat is provided.

Here are some examples of old and new ways to do the same
access control.

In this example, all requests are denied.

2.2 configuration:

Order deny,allow
Deny from all

2.4 configuration:

Require all denied

In this example, all requests are allowed.

2.2 configuration:

Order allow,deny
Allow from all

2.4 configuration:

Require all granted

In the following example, all hosts in the example.org domain
are allowed access; all other hosts are denied access.

2.2 configuration:

2.4 configuration:

Some other small adjustments may be necessary for particular
configurations as discussed below.

MaxRequestsPerChild has been renamed to
MaxConnectionsPerChild,
describes more accurately what it does. The old name is still
supported.

MaxClients has been renamed to
MaxRequestWorkers,
which describes more accurately what it does. For async MPMs, like
event, the maximum number of clients is not
equivalent than the number of worker threads. The old name is still
supported.

The DefaultType
directive no longer has any effect, other than to emit a
warning if it's used with any value other than
none. You need to use other configuration
settings to replace it in 2.4.

KeepAlive only
accepts values of On or Off.
Previously, any value other than "Off" or "0" was treated as
"On".

Directives AcceptMutex, LockFile, RewriteLock, SSLMutex,
SSLStaplingMutex, and WatchdogMutexPath have been replaced
with a single Mutex
directive. You will need to evaluate any use of these removed
directives in your 2.2 configuration to determine if they can
just be deleted or will need to be replaced using Mutex.

mod_cache: CacheIgnoreURLSessionIdentifiers
now does an exact match against the query string instead of a
partial match. If your configuration was using partial
strings, e.g. using sessionid to match
/someapplication/image.gif;jsessionid=123456789,
then you will need to change to the full string
jsessionid.

mod_cache: The second parameter to
CacheEnable only
matches forward proxy content if it begins with the correct
protocol. In 2.2 and earlier, a parameter of '/' matched all
content.

mod_ldap: LDAPTrustedClientCert is now
consistently a per-directory setting only. If you use this
directive, review your configuration to make sure it is
present in all the necessary directory contexts.

mod_reqtimeout: If the module is loaded, it
will now set some default timeouts.

mod_dumpio: DumpIOLogLevel
is no longer supported. Data is always logged at LogLeveltrace7.

On Unix platforms, piped logging commands configured using
either ErrorLog or
CustomLog were invoked using
/bin/sh -c in 2.2 and earlier. In 2.4 and later,
piped logging commands are executed directly. To restore the
old behaviour, see the piped logging
documentation.

mod_autoindex: will now extract titles and
display descriptions for .xhtml files, which were previously
ignored.

mod_ssl: The default format of the *_DN
variables has changed. The old format can still be used with the new
LegacyDNStringFormat argument to SSLOptions. The SSLv2 protocol is
no longer supported. SSLProxyCheckPeerCN
and SSLProxyCheckPeerExpire
now default to On, causing proxy requests to HTTPS hosts
with bad or outdated certificates to fail with a 502 status code (Bad
gateway)

The NameVirtualHost
directive no longer has any effect, other than to emit a
warning. Any address/port combination appearing in multiple
virtual hosts is implicitly treated as a name-based virtual host.

mod_deflate will now skip compression if it knows
that the size overhead added by the compression is larger than the data
to be compressed.

Multi-language error documents from 2.2.x may not work unless
they are adjusted to the new syntax of mod_include's
#if expr= element or the directive
SSILegacyExprParser is
enabled for the directory containing the error documents.

Invalid command 'User', perhaps misspelled or defined by a module not included in the server configuration - load module mod_unixd

Invalid command 'Require', perhaps misspelled or defined by a module not included in the server configuration, or
Invalid command 'Order', perhaps misspelled or defined by a module not included in the server configuration
- load module mod_access_compat, or update configuration to 2.4 authorization directives.

Ignoring deprecated use of DefaultType in line NN of /path/to/httpd.conf - remove DefaultType
and replace with other configuration settings.

Invalid command 'AddOutputFilterByType', perhaps misspelled
or defined by a module not included in the server configuration
- AddOutputFilterByType
has moved from the core to mod_filter, which must be loaded.

Notice:This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.